So, what's the difference? And what does this format skirmish mean to you? After all, both Blu-ray and HD, viewed on one of those $2,000, 1080p flat-screens, offer jaw-dropping visual clarity. Both formats will have theaters scrambling for higher quality, as evidenced by the wide release of Beowulf on IMAX and digital projection screens next month. Both Blu-ray and HD are backwards compatible, so you don't have to chuck the DVDs you already own. And both have a high level of interaction. Get bored watching Cars and you can actually play along with the movie. Want to know about Lightning McQueen and the history of the Ford GT40? Just push a button. If you've already spent all your lunch money for a PS3 or XBox 360, then you know about the interactivity afforded by Blu-ray and HD.